R1???(X???R2)a???R3 where R1 and R3 are the same or different and are H, H3C, OH, R2 or a reactive group (as described below); where R2 is a linear or branched substituted or unsubstituted alkyl group; where X is O (in which case the synthetic polymer may be a polyoxyalkylene) or X is NH(C???O) (in which case the synthetic polymer may be a polyamine), or X is absent (in which case the synthetic po